In many equipment service applications, it is sometimes necessary to splice the ends of two fluid lines together with a fluid-tight connection. This is particularly true in the service and repair of automotive air conditioning systems, where refrigerant lines, which usually are made of aluminum, have to be cut for various reasons such as, for instance, to remove a damaged or leaking section of the line. Many times, this has necessitated complete removal of the cut line and replacement with a new one, which can be expensive and inefficient. It also is desirable to install filters in refrigerant lines to filter out debris and small metal particles from the refrigerant. Couplers have been available to couple free ends of cut fluid lines together, but have not been completely satisfactory. Installing small thimble filters in an air conditioning refrigerant line also is known. However, a need exist for a fluid line connector, and particularly a connector for the refrigerant lines of automotive air conditioning systems, that is simple and fool-proof to install, that forms a reliable long-term fluid-tight seal around the ends of the coupled fluid lines, that provides the option of installing a refrigerant filter in-line with the refrigerant flow if desired, and that is modular and thus economical. It is to the provision of such a connector that the present invention is primarily directed.